The invention relates to a coil system and to a method for the contactless navigation of a magnetic body in a work space.
Coil systems for the contactless magnetic navigation of a magnetic body use a plurality of coils to produce a magnetic field which interacts with the magnetic body, whereby magnetic forces and torques are generated which cause the movement of the magnetic body. The magnetic force and the magnetic torque, which act on the magnetic body, can be suitably adjusted by way of the corresponding currents into the individual coils of the coil system.
Coil systems of the above type are used in particular in the medical field. Here a patient is examined in the work space of the coil system using the magnetic body. The work space is accessible from the outside and in this space the magnetic forces of the coil system have an adequate effect on the magnetic body. To carry out the examination the magnetic body, which is located in the patient, and the part of the patient's body to be examined are introduced into the work space of the coil system. The magnetic body is a probe with which measurements on—in particular images of—a patient's internal organs can be taken.
A coil system with magnetic probe is used, for example, in gastroenterology, in particular gastroscopy, see WO 2007/077922 A1. During the endoscopic examination the patient's stomach is partially filled with water and the patient swallows an appropriate probe which contains a permanent magnet and a camera.
Here the patient's stomach is located in the work space of the coil system or is introduced into the work space after the probe has been swallowed. By using the magnetic forces and torques generated by the coil system the probe is moved in such a way that images of the areas of the patient's gastric mucosa to be examined are produced. It is necessary in this connection for it to be possible by way of suitably energizing the coils to generate an inhomogeneous magnetic field such that the probe is appropriately positioned and is kept in this position by the interaction of this magnetic field with the permanent magnet in the probe.
Various approaches are known from the related art for appropriately positioning a magnetic body relative to a coil system. A coil system is known from WO 2006/014011 A1 in which, during the examination, the patient to be examined is moved in relation to the coil system. The coil system is constructed in such a way that a single spatial point exists which is fixed in relation to the coil system. If no external forces act on the magnetic body the body moves toward this spatial point as a result of the magnetic forces and torques exerted. When the magnetic body has reached this spatial point it remains there provided no forces are exerted from the outside. It has proven disadvantageous in this connection that either the coil system or the patient or both have to be mechanically moved in order to move the magnetic body. This is a problem in particular in applications in which rapid movement of the magnetic body toward a predetermined position is required.
Systems are also known from the related art in which the coil system is replaced by one or more permanent magnet(s) in order to move a magnetic body, see for example U.S. Pat. No. 7,019,610 B2. The movement toward a predetermined position is achieved by a mechanical movement of the patient or the permanent magnet or patient and permanent magnet in this system as well.
Coil systems are also known from the related art in which, without mechanical movement, by appropriate adjustment of the magnetic fields and field gradients, to the position of the magnetic body a movement of the magnetic body is achieved that is caused merely by the currents in the coil system (see for example WO 2006/092421 A1). However, it is necessary here for the position and orientation of the magnetic body to be known, and this in turn means that the position of the magnetic body also has to be measured.